1. Field of the Invention
The invention relates to an irradiation device and a method for the treatment of acne.
2. Brief Description of the Related Art
It is known to treat acne, which is a skin disease caused by proliferation of bacteria in blocked follicles of areas of the skin that are rich in sebaceous glands together with keratosis, with blue light in the range of 400-440 nm without significant proportions of UVA, with limited success.
Here we refer to the article of V. Sigurdsson et al., “Phototherapy of Acne Vulgaris with visible Light, Dermatologie 1997, 194; Iss. 3, 256-260” which includes further literature references. This form of therapy started by using red fluorescence of acne follicle as part of the dermatological examination using a woodlamp. The source determined for the fluorescence was the storage of large quantities of porphyrins in the propionbacterium acne. McGinley et al., Facial follicular porphyrin fluorescence. Correlation with age and density of propionibacterium acnes, Br. J. Dermatol. 1980, Vol. 102, Iss. 3, 437-441). Since the principal absorption (Soret-band) of porphyrins is around 420 nm, it was obvious for Meffert et al. to treat acne follicles with blue light. The longestwave absorption band of porphyrins is 630 nm, with a penetration depth of 4 mm, which is most favorable for photodynamic follicle treatment and is used for this purpose.
From WO 00/02491 such an irradiation device is known which comprises at least one narrowband spectrum in the range of 405-440 nm. As alternative or cumulative areas of the spectrum the wavelength intervals between 610-670 and 520-550 nm are given. For further improvement of treatment efficacy it is proposed to increase the oxygen concentration within the irradiated area by applying oxygen-enriched emulsions before or during the irradiation. The irradiation intensity for this is between 10-500 mW/cm2.
WO 00/64537 describes another irradiation device for the treatment of acne. Here the afflicted area is treated with UV light in the range of 320-350 nm. The energy input given here is 1-5 J/cm2. When using a laser, the pulse energy is supposed to be between 5-25 mJ/cm2, so that pulse lengths of 10 ns will result in an intensity of about 2 MW/cm2. The known irradiation device is based on the realization that sunlike spectra are not suitable for acne treatment, but may rather trigger an outbreak of acne.
From EP 0 565 331 B1 a device for the treatment of vascular diseases in an area of the skin is known, including a housing with an incoherent light source mounted in that housing and suitable for the emission of pulsed light for treatment, and an opening in the housing, defining a ray of light which is emitted onto the afflicted area of skin without passing through a cable of optical fibers, thus showing a wider irradiation area than devices with optical fibers, the device also including a low cutoff filter, thus cutting off the visible and UV parts of the spectrum while the incoherent light source emits a ray of light combining wavelengths between 300 and 1000 nm. The light source has an electrical connection to a pulse-forming-network in order to deliver a time pulse between 1 and 10 ms, the emitted ray of light producing an energy density between 30 and 100 J/cm2, so that the emitted light may pass through a low cutoff filter and penetrate the skin as deeply as desired without burning of the skin, in order to heat a blood vessel under the skin in the skin treatment area and to cause blood coagulation in the blood vessel.
The blood coagulation described there is to be avoided in the treatment of acne, so that the described device is not suitable for the treatment of acne or other superficial skin diseases.
From DE 93 21 497 U1 a therapeutic treatment device is known, which is operated with an incoherent light source emitting light pulses, a preferred embodiment using flash lamps which emit light in the range of 300-1000 nm. The aim of this method is also the coagulation of blood vessels. The energy density per pulse is between 30-100 J/cm2, so that we can refer to our comment concerning EP 0 565 331 B1.
Immunologic examinations of acne patients have shown no abnormal reactions, which leads to the assumption that immunologic processes are not a factor in the development of primary acne. A secondary factor is f. e. the rupture of the epithelia of the closed comedome that will allow the contents (ceratine cells, hairs, sebum, free fatty acids and bacteria) to come into contact with the connective tissue. This causes a foreign body reaction often accompanied by an acute inflammation of the skin, which is referred to as secondary inflammatory efflorescence.
After the subsiding of the inflammation, there is a third category of acne efflorescence showing a previous serious outbreak of acne, which is cosmetically disfiguring. These scars have different appearances, such as small and comedome-like, sunken-in like wormholes or keloid-like atrophic scars covering large areas.
The known irradiation arrangements for the treatment of acne are technically elaborate and therefore costly, especially if a high energy density in specified areas of the spectrum has to be produced.
Post-inflammatory acne efflorescences cannot be treated with known irradiation devices without tissue coagulation or ablation. Therefore the problem of acne scar therapy has not been satisfactorily solved so far. The excision of crateriform acne scars is invasive and goes with a high risk of infection. Facial acne scars can be treated with high-speed dermabrasion devices; keloid acne scars are often treated cryosurgically with liquid nitrogen. Both techniques are also elaborate as well as costly.